1. Field of the Invention
In a communication system, a shared uplink acknowledgment (ACK) channel can be communicated to a payload recipient in the payload message or a broadcast control channel. Reserving a dedicated time-frequency chunk for these short ACK messages and multiplexing different users to the same time slot with spreading codes having good cross-correlation properties can be used to accomplish such a shared uplink ACK channel. Recipient's ACK channel allocation information (time, frequency, spreading code) can be concatenated to the first message of the data transfer and/or whenever allocation should change. When multiple users are multiplexed into the same time-frequency allocation, overhead from short ACK messages can, thus, be avoided or reduced. This may be especially true in situations in which transmission preambles from different users consume system resources and the ACK message is still much shorter than minimum transmit opportunity allocation.
2. Description of the Related Art
In internet protocol (IP) based communications the link between a base station and a mobile station is usually unbalanced: most of the traffic is in one direction at a time. This same phenomenon also exists in relay and mesh networks. Simultaneous traffic in the opposite direction is usually just acknowledgement signals of successful (for which an ACK is used) or unsuccessful (for which a NACK is used) transmissions. Thus, the direction of transferred data consumes a lot of radio resources, but the other direction should not consume radio resources, since ACK messages are typically very short. Typical applications in which this kind of behavior can be seen are in the areas of downloading and web browsing. This principle can also apply to voice over IP (VoIP) or video communications when automatic repeat request (ARQ) is used with this kind of traffic. For convenience, ACK is used generically for description herein for both affirmative and negative acknowledgments, rather than referring both to ACK and NACK, although one of ordinary skill in the art would understand that a negative ACK is a NACK.